Adjustable Testing Tool and Method of Use

ABSTRACT

Methods and systems for testing a subterranean formation penetrated by a wellbore are provided. A testing tool has a plurality of packers spaced apart along the axis of the tool, and at least a testing port. The testing tool is positioned into the wellbore and packers are extended into sealing engagement with the wellbore wall, sealing thereby an interval of the wellbore. In some embodiments, the wellbore interval sealed between two packers is adjusted downhole. In one embodiment, the location of the testing port is adjusted between two packers. The methods may be used to advantage for reducing the contamination of the formation fluid by fluids or debris in the wellbore.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a non-provisional application of co-pendingprovisional application No. 60/845,332 filed on Sep. 18, 2006, andrelates to co-pending and commonly assigned U.S. patent application Ser.No. 11/562,908 filed Nov. 22, 2006; U.S. patent application No.60/882,701 filed Dec. 29,2006; and U.S. patent application No. 60/882359filed Dec. 28, 2006, the disclosures of which are hereby incorporatedherein by reference for all purposes.

TECHNICAL FIELD

The present invention relates to well testing tools and method of use.More particularly, the invention relates to testing tools having aplurality of packer elements and at least a testing port on the toolbody.

BACKGROUND OF THE INVENTION

Advanced formation testing tools have been used for example to capturefluid samples from subsurface earth formations. The fluid samples couldbe gas, liquid hydrocarbons or formation water. Formation testing toolsare typically equipped with a device, such as a straddle or dual packer.Straddle or dual packers comprise two inflatable sleeves around theformation testing tool, which makes contact with the earth formation indrilled wells when inflated and seal an interval of the wellbore. Thetesting tool usually comprises a port and a flow line communicating withthe sealed interval, in which fluid is flown between the packer intervaland in the testing tool.

Examples of such tools are schematically depicted in FIGS. 1A to 1D.FIG. 1A shows an elevational view of a typical drill-string conveyedtesting tool 10 a . Testing tool 10 a is conveyed by drill string 13 ainto wellbore 11 penetrating a subterranean formation 12. Drill string13 a has a central passageway that usually allows for mud circulationfrom the surface, then through downhole tool 10 a, through the bit 20and back to the surface, as known in the art. Testing tool 10 a may beintegral to one of more drill collar(s) constituting the bottom holeassembly or “BHA”. Testing tool 10 a is conveyed among (or may itselfbe) one or more measurement-while-drilling or logging while the tool(s)known to those skilled in the art. In some cases, the bottom holeassembly is adapted to convey a casing or a liner during drilling.Optionally, drill string 13 a allows for two-way mud pulse telemetrybetween testing tool 10 a and the surface. A mud pulse telemetry systemtypically comprises surface pressure sensors and actuators (such asvariable rate pumps) and downhole pressure sensors and actuators (suchas a siren) for sending acoustic signals between the downhole tool andthe surface. These signals are usually encoded, for example compressed,and decoded by surface and downhole controllers. Alternatively any kindof telemetry known in the art may be used instead of mud pulsetelemetry, such as electro-magnetic telemetry or wired drill pipetelemetry. Tool 10 a may be equipped with one or more packer(s) 26 a,that are preferably deflated and maintained below the outer surface oftool 10 a during the operations. When testing is desired, a command maybe sent from the surface to the tool 10 a via the telemetry system.Straddle packer 26 a can be inflated and extended toward the wall ofwellbore 11, achieving thereby a fluid connection between the formation12 and the testing tool 10 a across wellbore 11. As an example, tool 10a may be capable of drawing fluid from formation 12 into the testingtool 10 a, as shown by arrows 30 a. Usually one or more sensor(s)located in tool 10 a, such as pressure sensor, monitors a characteristicof the fluid. The signal of such sensor may be stored in downholememory, processed or compressed by a downhole processor and/or senduphole via telemetry. Note that in some cases, part of tool 10 a may beretrievable if the bottom hole assembly becomes stuck in the wellbore,for example by lowering a wireline cable and a fishing head.

FIG. 1B shows an elevational view of a typical drill-stem conveyedtesting tool 10 b. Testing tool 10 b is conveyed by tubing or drill pipestring 13 b into wellbore 11 penetrating a subterranean formation 12.Tubing string 13 b may have a central passageway that usually allows forfluid circulation (wellbore fluids or mud, treatment fluids, orformation fluids for example). The passageway may extend throughdownhole tool 10 b, as known in the art. Tubing or drill string 13 b mayalso allow for tool rotation from the surface. Testing tool 10 b may beintegral to one or more tubular(s) screwed together. Testing tool 10 bis conveyed among (or may be itself) one or more well testing tool(s)known to those skilled in the art, such as perforating gun. The testingtool 10 b may be lowered in an open hole as shown, or in a casedwellbore. In some cases, tubing string 13 b allows for two-way acoustictelemetry between testing tool 10 b and the surface, or any kind oftelemetry known in the art may be used instead, including conductivetubing or wired drill pipe. Tool 10 b may be equipped with one or morepacker(s) 26 b that is usually retracted (deflated) during tripping oftesting tool 10 b. When testing is desired, tool 10 b may be set intotesting configuration, for example by manipulating flow in tubing string13 b. Extendable packer 26 b can be extended (inflated) toward the wallof wellbore 11, achieving thereby a fluid connection between an intervalof formation 12 and the testing tool 10 b across wellbore 11. As anexample, tool 10 b may be capable of drawing fluid from formation 12into the testing tool 10 b, as shown by arrows 30 b. Usually one or moresensor(s) located in tool 10 b, such as pressure or flow rate sensor,monitor(s) a characteristic of the fluid. The signal of such sensor maybe stored in downhole memory, processed or compressed by a downholeprocessor and/or send uphole via telemetry. Note that in some cases partof tool 10 b may be a wireline run-in tool, lowered for example into thetubing string 13 b when a test is desired.

FIG. 1C shows an lavational view of a typical wireline conveyed testingtool 10 c. Testing tool 10 c is conveyed by wireline cable 13 cintowellbore 11 penetrating a subterranean formation 12. Testing tool 10 cmay be an integral tool or may be build in a modular fashion, as knownto those skilled in the art. Testing tool 10 c is conveyed among (or maybe itself) one or more logging tool(s) known to those skilled in theart. Preferably the wireline cable 13 c allows signal and powercommunication between the surface and testing tool 10 c. Testing tool 10c may be equipped with straddle packers 26 c, that are preferablyrecessed below the outer surface of tool 10 c during trippingoperations. When testing is desired, straddle packer 26 c can beextended (inflated) toward the wall of wellbore 11 achieving, thereby, afluid connection between an interval of formation 12 and the testingtool across wellbore 11. As an example, tool 10 c may be capable ofdrawing fluid from formation 12 into the testing tool 10 c, as shown byarrows 30 c. Examples of such tools can be found U.S. Pat. No. 4,860,581and U.S. Pat. No. 4,936,139, both assigned to the assignee of thepresent invention, and incorporated herein by reference. Note in somecases that wireline tools (and wireline cable) may be alternativelyconveyed on a tubing string, or by a downhole tractor (not shown). Notealso that the wireline tool may also be used in run-in tools inside adrill string, such as the drill string shown in FIG. 1A. In these cases,the wireline tool 10 c usually sticks out of hit 20 and may performmeasurements, for example when the bottom hole assembly is pulled out ofwellbore 11.

FIG. 1D shows an elevational view of another typical wireline conveyedtesting tool 10 d. Testing tool 10 d is conveyed by wireline cable 13 dinto wellbore 11 penetrating a subterranean formation 12. This timewellbore 11 is cased with a casing 40. Testing tool 10 d may be equippedwith one or more extendable (inflatable) packer(s) 26 d, that arepreferably recessed (deflated) below the outer surface of tool 10 dduring tripping operations. Tool 10 d is capable of perforating thecasing 40, usually below at least one packer (see perforation 41), forexample, the tool could include one or more perforating gun(s). In FIG.1D, the testing tool 10 d is shown drawing fluid from formation 12 intothe testing tool 10 d (see arrows 30 d). Usually one or more sensor(s)is located in tool 10 d, such as a pressure sensor, monitors acharacteristic of the fluid. The signal of such sensor is usually senduphole via telemetry. Note that in some cases, tools designed to test aformation behind a casing may also be used in open hole. Note also thatcased formations may be evaluated by downhole tool conveyed by othermeans that wireline cables.

Typical tools are not restricted to two packers. Downhole systems havingmore than two packers have been disclosed for example in patents U.S.Pat. No. 4,353,249, U.S. Pat. No. 4,392,376, U.S. Pat. No. 6,301,959 orU.S. Pat. No. 6,065,544.

In some situations, a problem occurs when fluid is drawn into the toolthrough openings along the tool body. Formation fluids, wellbore fluidsand other debris from the wellbore may occupy the volume between theupper sealed packer and the lower sealed packer. This causes variousfluids to enter the same openings (or similar openings) located in thesealed volume. Moreover, when the density of the wellbore fluid islarger than the density of the formation fluid, it is very difficult toremove all of the wellbore fluid since there will be a residual ofwellbore fluid that resides between the lowest opening and the lowestpacker, even after a log pumping time. Thus, these wellbore fluids cancontaminate the formation fluid entering the tool.

Downhole systems facilitating the adjustment of the flow pattern betweenthe formation and the interior of the tool have been disclosed forexample in patent application US 2005/0155760. These systems may be usedto reduce the contamination of the formation fluid by mud filtratesurrounding the wellbore. Note that methods applicable for reducing thecontamination by mud filtrate surrounding the wellbore are not alwaysapplicable for reducing the contamination by fluids and other debrisfrom the wellbore.

Despite the advances in formation testing, there is a need for improvedtesting methods utilizing a tool having plurality of packers spacedapart along the axis of the tool, and at lest a port on the tool bodylocated between two packer elements. Such methods are preferably capableof reducing the contamination of the formation fluid by fluid or debrisin the wellbore. These methods may comprise adjusting in situ the lengthof a sealed interval between two packer elements. Alternatively, thesemethods may comprise adjusting the location of the port within a packerinterval.

SUMMARY OF THE INVENTION

Methods and systems for testing a subterranean formation penetrated by awellbore are provided. A testing tool has a tool body, a plurality ofpacker elements spaced apart from one another along the longitudinalaxis of the tool body, and at least a testing port on the tool bodylocated between two packer elements. The testing tool is positioned intothe wellbore and packers are extended into sealing engagement with thewellbore wall, sealing thereby an interval of the wellbore. Fluid isflown between the sealed interval and the testing tool through thetesting port.

In at least one aspect, the invention relates to a method that comprisesthe steps of selecting in situ the length of an interval of the wellboreto be sealed, and extending at least two packer elements. The length ofthe interval of the wellbore that is sealed by extending the packerelements is substantially equal to the selected length.

In another aspect, the invention relates to a method that comprises thestep of extending at least two packer elements into sealing engagementwith the wellbore wall, sealing thereby a first interval of thewellbore. The method also comprises the step of extending another packerelement into sealing engagement with the wellbore wall, sealing therebya second interval of the wellbore.

In yet another aspect, the invention relates to a method that comprisesthe step of adjusting a port on a testing tool.

In yet another aspect, the invention relates to a system for testing asubterranean formation penetrated by a wellbore. The system comprises atesting tool and a snorkel assembly adaptable on the testing tool. Thesnorkel assembly comprises a snorkel port and a fluid communicationbetween the port on the tool body and the snorkel port, the snorkel portand the tool port being substantially offset from each other.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION Of THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIGS. 1A-1D are elevation views showing typical examples of downholetesting tools, where the testing tool is drill string conveyed in FIG.1A, tubing string conveyed in FIG. 1B, and wireline conveyed in FIGS. 1Cand 1D.

FIG. 2 is a schematic showing one embodiment of a testing tool capableof scaling wellbore intervals of various lengths;

FIG. 3 is a schematic illustrating the selective length adjustment of asealed wellbore interval with a tool having a plurality of spaced apartpacker elements;

FIG. 4 is a schematic illustrating the selective adjustment the lengthof a sealed wellbore interval with a tool having a slidable packerelement;

FIGS. 5A-5B are cross sectional views showing embodiments of a snorkelassembly adapted to a testing tool;

FIGS. 6A-6B show a flow chart describing the steps involved in oneembodiment of a method for testing a subterranean formation;

FIGS. 7A-7D are schematics illustrating a method for testing asubterranean formation;

FIGS. 8A-8D are schematics illustrating another a method for testing asubterranean formation; and

FIGS. 9A-9B are schematics illustrating yet another method for testing asubterranean formation.

DETAILED DESCRIPTION

Certain examples are shown in the above identified figures and describedin detail below. In describing these examples, like or identicalreference numbers are used to identify common or similar elements. Thefigures are not necessarily to scale and certain features and certainview of the figures may be shown exaggerated in scale or in schematicfor clarity and/or conciseness.

FIG. 2 shows one embodiment of a testing tool capable of sealingwellbore intervals of various lengths. The testing tool 10 is conveyedwithin wellbore 11 created in formation 12 via conveyance mean 13. Thetesting tool 10 can be conveyed downhole using a wireline cable afterthe well has been drilled and the drill string removed from thewellbore. Alternatively, the testing tool can be conveyed downhole onthe drill string used to drill the wellbore. Any conveyance mean knownin the art can be used to convey the tool 10. Optionally, the conveyancemean allows for two ways communication between tool 10 and the surface,typically a surface monitor (not shown), via a telemetry system as knownby those skilled in the art. When used with some conveyance means, tool10 may accommodate for mud circulation through the tool (not shown), aswell known by those skilled in the art. As shown in FIG. 2, the testingtool 10 is build in a modular fashion, with telemetry/electronics module154, packer module 100, downhole fluid analysis module 151, pump module152, and carrier module 153. Telemetry/electronics module 154 maycomprise a controller 140, for controlling the tool operation, eitherfrom instructions programmed in the tool and executed by processor 140 aand stored in memory 140 b, or from instruction received from thesurface and decoded by telemetry system 140 c. Controller 140 ispreferably connected to valves, such as valves 110, 111, 112, 113, 114,115 and 116 via one or more bus 190 running through the modules of tool10 for selectively enabling the valves. Controller 140 may also controla pump 130, collect data from sensors (such as optical analyzer 131),store data in memory 140 b or send data to surface using telemetrysystem 140 c. the fluid analysis module 151 may include an opticalanalyzer 131, but other sensors such as resistivity cells, pressuregauges, temperature gauges, may also be included in fluid analysismodule 151 or in any other locations in tool 10. Pump module 152 maycomprise the pump 130, which may be a bidirectional pump, or anequivalent device, that may be used to circulate fluid along the toolmodules via one or more flow line 180. Carrier module 153 can have aplurality of cavities, such as cavities 150-1, 150-2, to 150-n to eitherstore samples of fluid collected downhole, or transport materials fromthe surface, as required for the operation of tool 10. Packer elements102, 103, 104 and 105 are shown uninflated and spaced along thelongitudinal axis of packer module 100. Although not shown, the packersextend circumferentially around tool 100 so that when they are inflatedthey will each form a seal between the tool and a wellbore wall 15.

Also shown on FIG. 2 are particle breaking devices 160, 161, or 162.These particle breaking devices could be focused ultrasonic transducersor laser diodes. Particle breaking devices are preferably used topulverize sand, or other particles passing into the flow lines, intosmaller size particle, for example, for avoiding plugging of componentof the testing tool. These devices may use different energy/frequencylevels to target various grain sizes. For example, particle breakingdevice 162 may be used to break produced sand during a samplingoperation. In some cases, the readings of downhole sensor 131 will beless affected by pulverized particles than larger size particles. Inanother example, particle breaking device 163 may be used to breakparticles in suspension in the mud during an injection (fracturing)operation. In some cases, pump 130 will be able to handle pulverizedparticles more efficiently and will not plug, leak or erode as fast aswith larger size particles in the mud. Particle breaking devices may beused for other applications, such as transferring heat to the flow linefluid.

While testing tool 10, as shown in FIG. 2, is build in a modularfashion, those skilled in the art will appreciate that all thecomponents of tool 10 may be packaged in a single housing. Also, thearrangement of the modules in FIG. 2 may be modified. For example, fluidanalysis module 151 shown above pump module 152 may alternatively belocated between pump module 130 and carrier module 153. In somesituation, tool 10 can have additional (or fewer) operationalcapabilities beyond what is discussed herein. The tool can be used for avariety of testing, sampling and/or injection operations using theselectively enabled packer elements as discussed herein.

FIG. 3 shows in more details an embodiment of packer module 200 similarto module 100 of FIG. 2, where two of the four packer elements have beeninflated. Packer module or tool portion 200 may comprise one or moreflow line 280, similar to flow line 180 in FIG. 2. Flowline 280 isselectively connected to one or more port(s) in the tool, such as ports252, 253 a, 253 b and 254 via associated valves 242, 243 a, 243 b and244 respectively, allowing fluid to flow from or into flow line 280.Each interval between packer elements 262, 263, 264 and 265 haspreferably at least one port. Although shown on the same side of thetool, ports may be located anywhere around the tool. Packer module ortool portion 200 may also comprise packer inflation devices 212, 213,214 and 215 for selectively inflate or deflate packers 262, 263, 264,and 265 respectively. Other means to extend packers into sealingengagement with the wellbore wall may also be used without departingfrom the invention. Inflation devices 212, 213, 214 and 215 may consistof one or more pump(s), controlled by a controller (not shown) via bus290, similar to bus 190 of FIG. 2.

Note that testing tool 10 may not be modular. In this eventuality FIG. 3would represent a portion of testing tool 10. Note also that theconcepts discussed herein are not limited to four packer elements. Anynumber of packer elements may be deployed on a tool and selectivelyinflated depending on desired results and the operations to beperformed. Also note that the packer elements need not be all of thesame type or spaced equidistant from each other.

Each of the packers 262, 263, 264 and 265 can be inflated so that thepackers radially expand and contact wellbore wall 15 of formation 12. Byexpanding at least two of the packers sufficiently to contact thewellbore wall, the interval of the wellbore between the two inflatedpackers can be sealed off from the rest of the wellbore. Thus, as shownin FIG. 2, packers 263 and 265 have been selectively inflated to form asealed interval 221 between packers 263 and 265. The sealed intervalallows, for example, formation fluid to be drawn into the tool fortesting. The selective enabling of each packer can be, for example, byexpanding the packer under the control of inflation devices 212, 213,214 and 215 by hydraulic lines extending into the packer element. Notethat while each packer is shown with an individual inflation device, adevice common to each packer can be used. Also, the force for enablingthe packers can come from the surface or from another tool, if desired.

Other packers may be selectively extended to seal wellbore intervals ofvarious lengths. An interval length may be selected downhole, forexample by analyzing measurements performed by sensors of tool 10 orfrom another tool in the tool string. A measurement that may be used insome cases could be a wellbore resistivity image. By way of example, thelongest testing interval may be selected. Sampling a long interval ofwellbore wall in this way could result in a lower drawdown pressure. Theuser (or some logic implemented downhole) would then enable packers 262and 265, for example by activating inflation devices 212 and 215 throughbus 290. Packers 262 and 264 would not be enabled and would remainretracted (deflated). By extending packers 262 and 265, the wellboreinterval between top packer 262 and bottom packer 265 would be sealed.Testing would follow. For example, this may include injecting or drawingfluid from any of the ports 252, 253 a, 253 b or 254 by opening any ofthe associated valves 242, 243 a, 243 b or 244 respectively.Alternatively, a short testing interval may be selected. Sampling ashort interval of wellbore wall in this way could result in a morehomogenous fluid. For example, it may be desirable to only test aninterval having a length almost equal to the distance between packers263 and 264. This can be done by extending packers 263 and 264 towardthe wellbore wall and sealing the corresponding interval. Note that byhaving non-equal spacings between three or more packers, the user canchoose among a variety of interval length to be sealed and test theformation.

In some testing applications, monitoring the flow of fluids in theformation (injected from the tool or drawn into the tool) maybedesirable. In some situations, it can be advantageous to have sensors,such has sensors 201, close the wellbore wall 15. In one embodiment,sensors 201 a, 201 b, 201 c and 201 d may be located directly on thepackers. These sensors can measure various formation or fluid propertieswhile the tool is in the wellbore. For simplification. FIG. 3illustrates sensors 201 a -201 d only on packers 263 and 265. However,the sensors may also be located on any or all of the packers. Inaddition to locating the sensors on the packers, other sensors 202, suchas sensors 202 a, 202 b, and 202 c, may be located on or within the toolat any location. Some of these sensors 201, 202 may measure fluidproperties (such as pressure, optical densities) while others maymeasure formation properties (such as resistivity, sigma, carbon-oxygenratio, sonic travel time). Data gathered by sensors 201 a-d and 202 a-c(and other sensors) may be communicated via bus 290 to a controller (notshown) similar to the controller 140 of FIG. 2. The data sent to thecontroller may further by processed downhole by a processor, similar tothe processor 140 a of FIG. 2. The controller may further adjustoperations of the tool 10, for example modify the pumping rate of pump130 or modifying the length of the sealed interval, based on theprocessed data. Data gathered by sensors 201, 202 may also be storeddownhole into a memory, similar to the memory 140 b of FIG. 2, or sentuphole for analysis by an operator via a telemetry system, similar tothe telemetry system 140 c of FIG. 2.

Perforation may be desirable for some testing applications. Thus, theformation may further be perforated at a point within the sealed offinterval of the wellbore, for example, for altering the fluid flow fromthe formation to the sealed interval of the wellbore between the twoinflated packers. Any kind of perforation device may be mounted betweentwo inflatable packers, such as perforation guns 230 and 231. Forexample, a bullet fired from a perforating gun 230 may be used toperforate formation 12 as shown in FIG. 3 to create a perforation 222.The bullet may hold a sensor capable of sending data to tool 10, forexample using an electromagnetic wave communication.

FIG. 4 shows another embodiment of a testing tool capable of selectingin situ the length of an interval to be sealed. Thus, FIG. 4 illustratesthe selective length adjustment of a sealed wellbore interval by slidinga packer element along the length of the tool to vary the distancebetween two packer elements. Referring to FIG. 4, packer module 300similar to packer module 100 of FIG. 2 is shown. Packer module 300 isshown with three packer elements 360, 361 and 362 but any number ofpackers could be employed. These three packer modules are operativelycoupled with three inflation devices 310, 311 and 312 respectively forselectively extending (inflating) and recessing (deflating) the threepacker elements. The inflation devices 310, 311 and 312 may becommunicatively coupled to a downhole controller via a bus 390, similarto bus 190. In the embodiment of FIG. 4, the middle packer 361 is shownto be slidably movable along the longitudinal axis of the tool 10.Packer element 361 is coupled to piston actuator 302 which may beutilized to slide packer 361 up or down the length of the tool body. Forexample, actuator 302 could be used to move packer 361 to position 361.The fluid for inflating/deflating the packer could be delivered byinflation device 311 to packer 361, for example, via hydraulic linelocated in ram 303 (not shown).

In operation, testing tool 10 of FIG. 4 would be lowered into formation12 traversed by wellbore 11. The length of an interval of wellbore 11 tobe sealed can be determined in situ. For example, a Nuclear MagneticResonance measurement can be used to estimate the viscosity of theformation fluid surrounding tool 10, and the length of the interval tobe sealed for a sampling operation may be adjusted therefrom. The pistonactuator 302 may then be activated for sliding packer element 361 alongthe tool body for adjusting the distance between packer element 360 andpacker element 361. For example, once the length is selected (packerelement 361 is moved to position 361′ on FIG. 4), packer elements 360and 361 may be extended (inflated) toward the wellbore wall 15 byinflation devices 310 and 311, sealing thereby an interval of thewellbore which length is substantially equal to the selected length.Testing may then begin. For example, fluid may be drawn into the toolthrough port 351. The testing step may involve manipulating valves, suchas valve 341. Fluid may be flown into flowline 380 (similar to flowline180 in FIG. 2). When testing is finished, packers are usually deflatedbelow the outer surface of the testing tool.

The embodiment shown in FIG. 4 can be combined with the embodiment shownin FIG. 2 or FIG. 3, such that packers 102, 103, 104 and 105 (FIG. 2)may all be slidably moved along the tool such that it is possible tovary the vertical distance between any two packers. As an example, itmay be desirable to test a region of an earth formation larger than thatcovered by the area between packers 102 and 103 but not as large as theareas covered by packers 102 and 104. In this case, packer 102 could bemoved upward in the vertical directional along the tool to expand thetop area, or packer 103 may be moved downward in the vertical directionalong the tool to expand the area downward. The ability to selectivelymove packers in the vertical direction along the tool provides aninfinite number of testing regions within the well.

Note that some packers may be slidable and some may not, as shown inFIG. 4 by non slidable packer 360 and 362, and slidable packer 361. Notealso that slidable and non slidable packers may be arranged in variouscombinations. Although the operation of testing tool 10 of FIG. 4 hasbeen described using packer element 360 and 361 to seal an interval witha length selected downhole, packer 361 and 362 may be used instead, andfluid may alternatively be flown through port 352 (and open valve 342)on tool 10.

FIGS. 5A-5B show embodiments of a snorkel assembly 401 (FIG. 5A) and401′ (FIG. 5B) adapted to a testing tool 10. The snorkel assembly may beused to advantage for bringing a port of the sampling tool to a moreeffective relative position with respect to the packer elements. FIG.5A-5B show a packer module 400 adapted on a testing tool 10 lowered in awellbore 11 penetrating a formation 12. Note that the testing tool isshown partially, and may be similar to the testing tool of FIG. 2. Thetesting tool 10 may include controller bow springs 480 and 481 as knownin the art. The packer module 400 comprises packer elements 462 and 463for sealing an interval of the wellbore 11 by extending (inflating) thepacker elements into sealing engagement with the wellbore wall 15, forexample with inflation devices 412 and 4l3 respectively. The packermodule 400 may further comprise a port 450 on the tool body and anassociated valve 451. The port allows for fluid communication between aflow line 490 in the downhole tool, similar to flow line 180 in FIG. 2,and a sealed interval of the wellbore. In the examples of FIGS. 5A-5Btwo different snorkel assemblies 401 and 401′ respectively, are adaptedon the testing tool 10. The snorkel assembly 401 or 401′ may comprise afilter 423, an adapter 422, a snorkel 421 (FIG. 5A) or 421′ (FIG. 5B),and a ring 420. Note that the snorkel assembly may comprise additionalparts, such as sensors, for providing other functionalities. Note alsothat the snorkel assembly may comprise fewer parts. For example thefilter 423, the ring 420, may be optional.

The snorkel assembly is preferably adaptable on the testing tool 10. Forexample, while the packer module 400 is disconnected from the testingtool 10, and the packer element 462 is not mounted on the packer module,the adapter 422 may slide around the packer module body and rest on themounted packer 463. When the adapter 422 is in place, the port 450 ofthe tool is fluidly connected to annular groove 431 of the adapter 422.Then the snorkel 421 or 421′ is slid on top of the adapter 422. Snorkel421 (421′) comprises one or more fluid communication(s) 440 (440′)between a snorkel port 430 (430′) and annular groove 431 via one or morepassageway 441. In the example of FIGS. 5A-5B, fluid communication(s)440 comprise a plurality of flow lines, for example eight, distributedaround the circumference of the snorkel. A screen filter 423 may thenslide around the snorkel and may be held in place with screws 470 orother fasteners. The filter 423 preferably covers the snorkel port 430(430′). A ring 420 may finally be slid on the tool mandrel and locked inplace before the packer element 462 is mounted. The packer module 400 isfurther included into testing tool 10. The testing tool 10 may belowered into a wellbore to perform a test on a subterranean formation.

Different snorkel designs may have different snorkel portconfigurations. The snorkel design that is adapted on tool 10 ispreferably chosen such that the snorkel port configuration is adjustedfor a particular testing operation. In the example of FIG. 5A, thesnorkel port 430 is shown higher than the snorkel port 430′ of FIG. 5B.Also the snorkel port shape may be adjusted from one snorkel design toanother. Thus, if a snorkel port configuration such as shown by 430 isdesirable for testing, an operator may adapt the snorkel 421 to thetesting tool 10, adjusting thereby the initial configuration of the porton the testing tool 450 to the desired configuration of the snorkel port430. In other cases, a different snorkel port configuration, such asshown by 430′, may be desirable for testing. Here again, an operator mayadapt a different snorkel to the testing tool 10, adjusting thereby theinitial configuration of the port on the testing tool 450 to thedifferent configuration of the snorkel port 430′.

Screen filters with various characteristics can be assembled in thesnorkel assembly. In some cases, the screen filter may comprise two ormore screens. In some cases, the screens may be separated by a smallgap. Also the screens can be reinforced, for example by vertical strips.The screen filter characteristics are preferably adjusted for thetesting operation the tool is intended to perform.

Note that a snorkel assembly can be adapted to any kind of testing tool,such as the testing tool of FIG. 2, 3 or 4. Note also that the snorkelin the snorkel assembly could be made telescopic and may be adjusteddownhole using an actuator.

FIGS. 6A-6B describe one embodiment of a method 500 for testing asubterranean formation. The method 500 preferably utilizes a testingtool having a tool body, a plurality of packer elements spaced apartfrom one another along the longitudinal axis of the tool body, and atleast a testing port on the tool body located between two packer, as isthe described herein. However, the method 500 may be used with anytesting tool having selectively-activated packer elements and capable offormation testing.

In optional step 505, a snorkel assembly is placed on the testing tool.The snorkel assembly is capable of adjusting a port on a testing tool.The snorkel assembly may also be capable of adjusting the characteristicof a filter screen. The snorkel may further be capable of reducing thevolume trapped in the sealed interval. For example, the testing tool maybe intended to sample formation fluid in an unconsolidated formation,and the formation fluid is expected to have a lower density than theborehole fluid. The testing tool may also be intended for a largediameter wellbore. Such sampling situation is illustrated in FIG. 9A-9Bfor explanatory purposes. Note that in step 505 of method 500, thetesting tool is not yet lowered into the borehole, and FIG. 9A-9B areused therebelow to explain how the testing tool is expected to performin the sampling situation discussed above, based on a prior knowledge ofthe sampling conditions, and how the adjustment of step 505 may beperformed.

Referring to FIG. 9A, a portion of testing tool similar to testing tool10 of FIG. 2 is shown in a wellbore 11 traversing a formation 12 duringa sampling operation. Packer elements 862 and 863 are shown in anextended position, and engaged with the wellbore wall 15 for sealing awellbore interval therebetween. In the example of FIG. 9A, the testingtool 10 has drained fluid from the wellbore into flowline 890 (similarto flow line 180 of FIG. 2) through tool port 850 and open valve 851.The fluid drained from the wellbore has been partially replaced byformation fluid 842, and sand or debris 840 produced from the formation.Note that some wellbore fluid may still be present in the sealedinterval, as shown by wellbore fluid 841. The illustration of FIG. 9Aassumes that debris, wellbore fluid and formation fluid have segregatedin the order as shown, because of the density contrast between thesematerials. However segregation may occur in a different order. Duringthe sampling operation shown in FIG. 9A, sand or debris may enter toolport 850 and plug, clog or erode various components in the testing tool10, such as pumps, or valves. Also, debris may cause noise at a fluidproperty sensor. Finally, the volume of the sealed interval may belarge, because the testing tool is run in a wellbore of large diameter.Because of this large volume, the sampling operation may require a logtime before formation fluid enters in the testing tool and is availablefor capture in a cavity. This long sampling time may increase theprobability of the testing tool to become stuck in the wellbore.

Turning now to FIG. 9B, a snorkel assembly 800 is shown in a wellbore 11traversing a formation 12 during a sampling operation similar to thesampling operation shown in FIG. 9A. Ib FIG. 9B the location of the toolport 850 has been adjusted for this particular operation by adapting asnorkel assembly to the testing tool prior to lowering it into theborehole. Fluid is now drawn from the wellbore at the snorkel port 830.Snorkel port 830 is located above the debris that have segregated on topof the lower packer element 863, reducing thereby the probability ofcomponents of the tool 10 being plugged by debris entering the testingtool 10. Note also that the snorkel port is located close to the upperpacker element 862, reducing thereby the volume and the time needed todraw into the tool formation fluid that has segregated above thewellbore fluid. In the example of FIG. 9B, the snorkel assembly alsocomprises a filter screen 823, whose characteristics such as the area,the screen mesh size, the number of screen layers or the screen collapseresistance may have bene adjusted to the sampling operation. Forexample, the screen filter 823 may be chosen to be a double layerfilter, or may be reinforced by vertical stripes between the layers toinsure a high collapse resistance. The snorkel port 830 may furtherextend around the entire circumference of the tool, increasing therebythe area of the intake adjacent to the filter screen, which may beadvantageous for avoiding plugging of the filter screen. In the exampleof FIG. 9B, the outside diameter of the snorkel module has been selectedso that the trapped volume of fluid between packer element 862 and 863is reduced with respect to FIG. 9A. Specifically, the outside diameteris selected just below the wellbore diameter. Reducing the trappedvolume of fluid may decrease the volume of fluid needed to be pumpedbefore formation fluid enters the tool and decreases the time needed tocapture a formation fluid sample. Note that the volume may also bereduced by using rings, such as ring 820.

Turning back to FIGS. 6A-6B, the testing tool is lowered in the wellborein step 510. As mentioned before, the testing tool may be conveyed on adrill string, a tubing string, a wireline cable or any other means knownby those skilled in the art. Lowering the downhole tool may comprisedrilling or reaming the wellbore. The wellbore may be open to theformation or may be cased. If the wellbore is cased, the testing toolpreferably comprises perforation devices, such as the shafts orperforating guns, for example located between two packer elements. Thetesting tool may be lowered in the wellbore with other tools, such asformation evaluation tools known by those skilled in the art. Theconveyance means preferably comprises a telemetry system capable ofsending information collected by a downhole tool to the surface, andreceiving commands from the surface for controlling operation of thetesting tool. A downhole controller executing instructions stored in adownhole memory in the testing tool may also control operations of thetesting tool.

Step 515 in FIGS. 6A-6B determines the length of the wellbore intervalto be tested. This can be achieved downhole, for example using aprocessor and data collected by sensors. This can alternatively beachieved under control of a user operating from the surface, forexample, using a camera or other sensing tools, not shown, which arepart of the downhole tool string. This can be alternatively achieved byany other methods and/or sensors mentioned therein. Other methods and/orsensors may also be used without departing from this invention. Themethod 500 may comprise the optional step 520, that determines whethercleaning is desired within the testing interval. Cleaning may comprisedelivering materials conveyed from the surface in one of the cavity oftesting tool 10, such as cavity 150-1 of FIG. 2, into the wellbore, forexample for dissolving locally the mudcake on the wellbore wall 15. Thismaterial could be water, steam, acid solution, solvent or anycombination thereof. If cleaning is desired, optional step 525determines the length of a cleaning interval to be sealed, usuallycomprising the testing interval so that the cleaning material can befully removed from the testing interval as further discussed below. Thecleaning interval length may be selected by enabling the extension oftwo packer elements from the plurality of the packer elements carried bythe testing tool in step 530. Note that the adjustment of the testinginterval length may alternatively be achieved by sliding packer elementsalong the axis of the tool prior to extending the packer element towardthe wellbore wall, as previously discussed with respect to FIG. 4.

As a way of example, FIGS. 7A-7D show a portion of a testing toolsimilar to testing 10 of FIG. 2, lowered in a wellbore 11 traversing aformation 12. The testing tool 10 comprises packer elements 602, 603,604 and 605, and ports 652, 653, and 654. In the example of FIGS. 7A-7D,the extension of packer elements 602, 603, 604 or 605 can be selectivelyenabled, for example using the apparatus described in more details withrespect to FIG. 3. As a way of example, the length of the wellboreinterval to be sealed determined in step 515 may be represented byinterval 610 on FIGS. 7A-7D. As a way of example, the length of thewellbore interval to be sealed determined in step 525, may berepresented by interval 611 on FIGS. 7B-7D.

Turning back to FIGS. 6A-6B, packer elements of the testing tool areextended toward the wellbore wall in step 535 if cleaning is desired. Afirst interval, the cleaning interval, is sealed from the rest of thewellbore in step 540. Note that in some cases it may be advantageous tobypass one of the sealing packer element with a flow line (not shown) inthe testing tool that establishes a fluid communication between thesealed interval in step 540 and another part of the system, for examplethe wellbore outside the sealed cleaning interval. Optional cleaning ortreatment is performed in step 545.

In the example of FIGS. 7B and 7C, the interval length may be selectedby enabling the extension of two selected packer elements from aplurality of packer elements carried by the testing tool. Packers 602and 604 are first enabled and then extended (inflated) in step 535 ofthe method shown in FIGS. 6A-6B. By extending toward the wellbore wall,packers 602 and 604 seal the cleaning interval 611 which length isroughly equivalent to the determined length in step 525 of the method500 shown in FIGS. 6A-6B. A cleaning fluid 660 may then be injectedthrough port 652 or 653 into the wellbore in step 545 of the methodshown in FIGS. 6A-6B. Preferably the cleaning fluid 660 will occupy alarge portion of the cleaning interval, as indicated by cleaning fluid660 in FIG. 7B. Sensors, similar to sensors 202 a-c or 201 a -d shown inFIG. 3, or other sensors, may optionally monitor the cleaning process,and the cleaning process may be controlled based on the sensor signals.Step 545 may further comprise draining the cleaning fluid 660, forexample in port 653 as shown in FIG. 7C. This cleaning fluid may bedumped into the wellbore outside the sealed interval, for example atport 163 of FIG. 2, or stored in a cavity in the testing tool, suchcavity 150-2 of FIG. 2. Usually, draining through port 653 will notefficiently remove the cleaning fluid 660 located between the lowerpacker element of the sealed interval 604 and the draining port 653.Note that in the example of FIG. 7C, it is assumed that the density ofthe cleaning fluid and/or cleaning debris is larger than the density ofthe formation fluid. It is further assumed that the testing tool 10 isoperated such that formation fluid is drawn from the surroundingformation as cleaning fluid is drained outside the cleaning interval, asshown by formation fluid 661. Thus, formation fluid and cleaning fluidmay segregate by gravity as shown in FIG. 7C. In the case the formationfluid density is higher than the cleaning fluid and/or cleaning debrisdensity, the sequence of formation fluid, cleaning fluid, and/orcleaning debris may be different. Note also that this invention is notlimited to the presence of two segregated fluids in the sealed interval.

Turning back to FIGS. 6A-6B, the testing interval length may be selectedby enabling the extension of two packer elements from the plurality ofthe packer elements carried by the testing tool in step 550. Note thatthe adjustment of the testing interval length may alternatively beachieved by sliding packer elements along the axis of the tool prior toextending the packer element toward the wellbore wall, as previouslydiscussed with respect to FIG. 4. Packer elements of the testing toolare extended toward the wellbore wall in step 555. Note that if a firstcleaning interval has already been sealed, it may be advantageous insome cases to maintain the first interval sealed while sealing a secondinterval, the testing interval. Thus, it may be advantageous to bypassone of the sealing packer element with a flow line (not shown) in thetesting tool that establishes a fluid communication between the cleaninginterval and another part of the system, for example the wellboreoutside the sealed cleaning interval. This would allow for the fluiddisplaced by the extension of a third packer element in the sealedinterval to be vented out of the sealed interval. A testing interval issealed from the rest of the wellbore in step 560. Testing of theformation is performed in step 565, for example injection, sampling, orlocal interference test (also known as interval pressure transient testor IPTT) is preferably performed in a manner known in the art.

Continuing with the example of FIG. 7D, the testing interval 610 isselected by enabling the extension (inflation) of packer element 603between already extended packer elements 602 and 603 (step 550 of themethod in FIGS. 6A-6B). Note, that in this scenario packer element 602would be enabled for both sealing the testing volume and the cleaningvolume. The testing interval 610 is sealed once the packer element 603reaches the wellbore wall. Thus, the testing interval 610 is nowisolated from the residual cleaning material and/or debris 660 above thelower packer 604. The residual cleaning material and/or debris 660 isretained below expanded packer 603 and is trapped, so as not tocontaminate the fluid contained in the testing interval 610. However, ifdesired, packer 604 can be retracted (deflated) thereby allowing theresidual cleaning material to disburse downhole if desired. Testing maythen begin. Formation fluid may be drawn from interval 610 into the port652. Note that cleaning fluid 660 was drained during the cleaning periodthrough port 653 and formation fluid 661 is now drawn through port 652during the testing period. This may be achieved by associating port 652and 653 with valves (not shown), similar to valves 242 and 243associated respectively to ports 252 and 253 in FIG. 3.

Turning back to FIGS. 6A-6B, one or more additional interval may besealed if needed, including the option of selecting of the length ofthese additional intervals, as shown by step 570. Also, additionaltesting may be performed as shown by step 575. At any time, the operatoror internal logic may decide to abort the cycle and terminate the test.All the packer elements are preferably retracted (deflated) in step 580and the testing tool is free to move in the wellbore. Other methods thanmethod 500 may also benefit from sealed interval of adjustable length.These methods include, but are not limited to, injecting materials intothe formation, or formation testing to determine for example pressureand mobility of hydrocarbons in a reservoir. As mentioned above, a localinterference test (also known as interval pressure transient test ofIPTT) may benefit from sealed interval of adjustable length. Thepressure in sealed intervals of variable length may be pulsed. Thepressure pulse may be detected at a probe located above or below thesealed interval (similar to probe 16 c in FIG. 1C), that is in pressurecommunication with the formation.

FIGS. 8A-8D show another illustration of a method for testing asubterranean formation according to one aspect of this invention. FIGS.8A-8D show a portion of a testing tool similar to testing tool 10 ofFIG. 2, lowered in a wellbore 11 traversing a formation 12, as taught bystep 510 of method 500. Testing tool 10 comprises packer elements 702,703, 704 and 705, and ports 752, 753, 754 and 755. In the example ofFIGS. 8A-8D, packer elements 703 is slidable, for example using theapparatus described in more details with respect to FIG. 4.

As a way of example, the length of the wellbore interval to be sealeddetermined in step 515 of method 500 may be represented by interval 770on FIGS. 8A-8D. As taught by step 550 of method 500, the testinginterval length may then be selected by sliding packer element 703 asindicated by arrow 730 on FIG. 8A. The movement of packer element may becontrolled by a downhole controller (not shown), either automaticallyaccording to instructions executed by the downhole controller, or underthe supervision of a surface operator sending a command to the testingtool. The command sent to the testing tool could comprise a value of thetesting interval length determined by the operator, for example in viewof information recorded by downhole sensors (not shown) and sent upholeby a telemetry system (not shown).

FIG. 8B illustrate a first testing operation. In the example of FIG. 8B,packer elements 702 and 703 have been extended into sealing engagementwith the wellbore wall 15 (step 555 of method 500) and the testinginterval 770 is isolated (step 560 of method 500). The testing operation(step 565 of method 500) may comprise the optional step of perforatingthe formation as shown by tunnel 722 in formation 12. Perforation may beachieved by perforating guns, such as perforating gun 231 of FIG. 3, orby any other method known by those skilled in the art. Note that theperforation of the formation 12 about the testing interval 770 may beperformed before or after inflation of the packer elements 702 and 703.The testing operation shown in the example of FIG. 8B comprisesinjecting material through the port 752, for example steam, hot water,acid or solvent, into the testing interval 770 and the formation 12.Injection of steam, hot water or solvent may be desirable for example tolower viscosity of heavy hydrocarbon in formation 12 prior to sampling.Injection may also be desirable for testing the compatibility of theinjected fluid with the formation or reservoir fluid. The injectedmaterial may be conveyed downhole in a cavity (not shown), similar tocavity 150-1 in FIG. 2, or may also be conveyed from the surface intothe conveyance mean 13 b, as explained above with respect to FIG. 1B.The testing operation preferably allows for the injected material todiffuse in the formation 12, as indicated by arrows 731. During thissoaking period, various sensors (not shown) may measure formation offluid properties, such as fluid temperature, fluid pressure, orformation resistivity profile along the radial, axial or azimuthaldirection of the wellbore.

FIGS. 8C and 8D illustrate an optional testing operation following theinjection described in FIG. 8B. The length of a second testing intervalcan be selected, for example from the set of the distance between packerelement 703 and 704, the distance between packer 703 and 705 or thedistance between packer 704 and 705. In the example of FIG. 8C, a secondtesting interval 771 between packer elements 705 and 703 is sealed, astaught by step 570 of method 500. Alternatively, packer element 704 mayhave been enabled instead of packer element 705, sealing thereby asecond testing interval with a shorter length. The testing tool maystart drawing fluid from interval 771 may be replaced by sand 763,produced by an unconsolidated formation, and formation fluid 762, asindicated by arrows 732. Note that in the example of FIG. 8C, it isassumed that the density of the formation fluid 762, for example heavyoil, is larger than the density of the wellbore fluid 761, for examplewater. Note also that formation fluid 762 may be contaminated byinjection materials or other materials.

FIG. 8D shows the continuation of the sampling process started in FIG.8C. In FIG. 8D, an alternate fluid communication with the testing toolis established through port 754 by selectively opening a valve (notshown) associated with port 754, for example a valve similar to valve243 b of FIG. 3, and by closing a valve (not shown) associated with port753, for example a valve similar to valve 243 a of FIG. 3. Thisoperation may be initiated by a surface operator, for example in view offluid properties measured by the testing tool, for example by a sensorsimilar to sensor 131 of FIG. 2, and send uphole via telemetry. Thisoperation may alternatively be initiated by a downhole controller. Thus,formation fluid 762 may enter the testing tool through port 754,indicated by arrows 733. In the example of FIG. 8D, packer element 704has not been inflated, increasing thereby the risk of particles, such assand or other debris, to enter the testing tool via port 754. In somecases, there may still be particles in suspension in formation fluid754. It may be advantageous to pulverize these particles with particlebreaking devices, such as particles breaking devices 160, 161 or 162 onFIG. 2. Formation fluid may then be analyzed by one or more sensor inthe testing tool and/or captured in a cavity in the testing tool andbrought to the surface for further analysis, as known by those skilledin the art.

In the example of FIG. 8C, the second testing interval 771 is locatedbelow the first interval, for example to take advantage of gravityduring a sampling operation of a heavy hydrocarbon in formation 12. Itwill be appreciated by those skilled in the art that a second testinginterval may have alternatively be chosen above the first interval, forexample by extending initially packer elements 704 and 705 for sealingthe first testing interval. Alternatively, the second testing intervalmay comprise the first testing interval, for example by extending packerelement 704 and retracting packer element 703.

Although the present invention and its advantages have been described indetail, it should b understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

1. A method for testing a subterranean formation penetrated by awellbore, the method comprising: positioning the testing tool in thewellbore, the testing tool comprising a tool body, a plurality of packerelements spaced apart from one another along the longitudinal axis ofthe tool body, and at least one port on the tool body located betweentwo of the plurality of packer elements; selecting in situ the length ofan interval of the wellbore to be sealed; extending at least two packerelements into sealing engagement with the wellbore wall; sealing theinterval of the wellbore with the two packer elements; and flowing fluidbetween the sealed interval and the testing tool through the port. 2.The method of claim 1 wherein selecting in situ the length of aninterval on the wellbore wall to be sealed comprises sliding a packerelement along the longitudinal axis of the tool body.
 3. The method ofclaim 1 wherein the downhole tool further comprises at least threepacker elements; and selecting in situ the length of an interval on thewellbore wall to be scaled comprises selectively enabling the extensionof a first and a second packer elements.
 4. The method of claim 1wherein the downhole tool further comprises a plurality of portsassociated to a plurality of valves; and the method further comprisesselectively opening a valve to establish the fluid communication throughthe port associated with this valve.
 5. The method of claim 3 furthercomprising extending a third packer element into sealing engagement withthe wellbore wall.
 6. The method of claim 5 wherein the third packerelement is located between the first and second packer elements.
 7. Themethod of claim 6 wherein the downhole tool further comprises aplurality of ports associated to a plurality of valves; and the methodfurther comprises selectively opening a valve to establish the fluidcommunication through the port associated with this valve.
 8. The methodof claim 1 wherein the selecting in situ the length of an interval onthe wellbore wall to be sealed is based on the value of a measuredproperty by a downhole tool.
 9. The method of claim 1 further comprisingpulverizing particles carried by the fluid flowed through the port. 10.A method for testing a subterranean formation penetrated by a wellbore,the method comprising: positioning a testing tool in the wellbore, thetesting tool comprising a tool body, a plurality of packer elementsspaced apart from one another along the longitudinal axis of the toolbody, and at least one port on the tool body located between two of theplurality of packer elements; extending at least two packer elementsinto sealing engagement with the wellbore wall; sealing a first intervalof the wellbore; flowing fluid between the first sealed interval and thetesting tool through the port; extending a third packer element intosealing engagement with the wellbore wall; and sealing a second intervalof the wellbore.
 11. The method of claim 10 further comprising flowingfluid from the second sealed interval into the testing tool through theport.
 12. The method of claim 10 wherein the second interval beingcomprised in the first interval.
 13. The method of claim 10 wherein thedownhole tool further comprises a plurality of ports; the method furthercomprises flowing fluid from the second sealed interval into the testingtool through another port.
 14. The method of claim 10 wherein thedownhole tool further comprises a cavity in fluid communication with theport on tool body, the cavity carrying a material; and flowing fluidbetween the first sealed interval and the testing tool through the portcomprises releasing the material in the wellbore.
 15. The method ofclaim 10 wherein the downhole tool further comprises a cavity in fluidcommunication with the port on tool body; and flowing fluid between thefirst sealed interval and the testing tool through the port comprisesdrawing fluid into the cavity.
 16. The method of claim 10 wherein thedownhole tool further comprises a sensor; and the method furthercomprises monitoring a property with the sensor.
 17. The method of claim16 further wherein extending another packer element into sealingengagement with the wellbore wall is triggered by the monitoredproperty.
 18. The method of claim 10 further comprising pulverizingparticles carried by the fluid flowed through the port.
 19. A method fortesting a subterranean formation penetrated by a wellbore, the methodcomprising: adjusting a port on a testing tool, the testing toolcomprising a tool body, a plurality of packer elements spaced apart fromone another along the longitudinal axis of the tool body, and at least aport on the tool body located between two of the plurality of packerelements; positioning the testing tool in the wellbore; extending atleast two packer elements into sealing engagement with the wellborewall; sealing an interval of the wellbore; and draining fluid from thesealed interval into the testing tool through the adjusted port.
 20. Themethod of claim 19 wherein the testing tool further comprises a screenfilter; and the method further comprises adjusting a characteristic ofthe screen filter.
 21. The method of claim 19 further comprisingreducing the fluid volume trapped in the sealed interval by selectingthe outer diameter of the snorkel assembly.
 22. The method of claim 19wherein adjusting a port comprises adjusting the location of the portwithin a packer interval.
 23. The method of claim 19 wherein adjusting aport on a testing tool comprises adapting a snorkel assembly on thetesting tool, the snorkel assembly comprising a snorkel port and a fluidcommunication between the port on the tool body and the snorkel port,the snorkel port and the tool port being substantially offset from eachother.
 24. A system for testing a subterranean formation penetrated by awellbore, the system comprising: a testing tool comprising a tool body,a plurality of packer elements spaced apart from one another along thelongitudinal axis of the tool body, and at least a port on the tool bodylocated between two packer elements; and a snorkel assembly adaptable onthe testing tool comprising a snorkel port and a fluid communicationbetween the port on the tool body and the snorkel port, the snorkel portand the tool port being substantially offset from each other.
 25. Thesystem of claim 24 further comprising a screen filter.
 26. The system ofclaim 24 wherein the snorkel port is located at a different level withrespect to the longitudinal axis of the tool body than the port on thetool body.
 27. The system of claim 24 wherein the snorkel port extendsaround the circumference of the tool.
 28. The system of claim 24 furthercomprising: a flow line in the testing tool, the flow line being influid communication with the port on the tool; and an ultrasonictransmitter for emitting a wave in the flow line.
 29. The system ofclaim 24 further comprising: a flow line in the testing tool, the flowline being in fluid communication with the port on the tool; and a laserdiode for emitting a wave in the flow line.